we are three danish students carring out a technologyproject, concerning the desinfection of chicken eggs. we plan to desinfect the eggs with Ultra Violet energetic radiation. what we need to know is: can salmonella, and E-coli bacteria survice high frequency UV radiation? does it kill them, or do they have a defense system for this kind of attack?

They use uv light (180 or 256 nm, typically) as well as filtration to sterilize water for either aquarium use or manufacturing processes where water purity is important—like the food and pharmaceutical industries, for instance. Different bacteria require different uv doses to achieve near 100 % killing. Here is one reference with a table of doses for various organisms in water.

Your samples will be sitting on the surface of an egg, so your required doses may not be exactly the same, but at least this will give you a set of ball-park doses to consider. Your problem will also be to make sure that all of the egg surface gets the correct dose of uv light.

blcr11 already stated the most important, but yes bacteria do have repair system to protect them from UV damages, at least to some extent. Thus depending on the system, different bacterial species have different sensitivity to UV and enough light can kill them.

Good luck with devising a system that will provide enough intensity on all the eggs though, if you want efficient killing. And another thing to consider: the data in the table are given for free floating bacteria in water. But biofilms can increase resistance dramatically to a number of agents, I am not sure if UV are among them (although I suppose they are), and I am not sure how much E. coli and Salmonella biofilm are on the eggs, but that should nevertheless be considered, if you really want efficient sterilization.

Patrick

Science has proof without any certainty. Creationists have certainty without
any proof. (Ashley Montague)